Removal of cyanobacterial blooms in Taihu Lake using local soils II. Effective removal of Microcystis aeruginosa using local soils and sediments modified by chitosan

Abstract

Chitosan modification can turn many solids, such as local clays and soils, into highly effective flocculants in removing harmful cyanobacterial blooms in freshwaters. AbstractAfter sepiolite was modified with Fe 3C to increase its surface charge, the initial algal removal rate increased significantly, but its Q 8 h was not improved substantially at clay loadings below 0.1 g/L. Modification on netting and bridging properties of clays by either chitosan or polyacrylamide (PAM) dramatically increased flocculation (Q 8 h ) of MA cells in freshwaters. Algal removal efficiencies of different solids, including Type III clays, local soils and sediments, were all improved to a similar level of O90% at a total loading of 0.011 g/L (contained 0.001 g/L chitosan) after they were modified with chitosan, making the idea of clearing up algal blooms using local soils/sediments possible. The mechanism of netting and bridging was confirmed to be the most important factor in improving the removal efficiency of cells, whereas clays also played important roles in the sedimentation of the floc.

Influence of zeta potential on the flocculation of cyanobacteria cells using chitosan modified soil

“…However, the main mechanism of chitosan to remove particles in water was the long polymer chain with netting and bridging function (Huang and Chen, 1996;Zou et al, 2006), which was significantly different from the aluminium sulfate functioned mainly as a charge neutralizer, the results and mechanism on how the ZP affect the removal efficiency of chitosan may be also different. …”

“…For example, when Microcystis aeruginosa (M.A. ), the main species forming cyanobacteria blooms in Lake Taihu was firstly harvested from the culture medium by centrifugation and then re-dispersed into 0.5% NaCl solution, Zou et al (2006) reported that 80% of the algal cells were removed by 1 mg/L chitosan modified 10 mg/L soil in 30 min. However, if directly flocculated in the culture medium, maximally 60% were achieved in 4 hr with the same dosage (Li and Pan, 2013).…”

“…However, both exciting and unsatisfactory results of the algae removal using chitosan modified soil have been reported (Li and Pan, 2013;Zou et al, 2006). The changes of algal surface charge attributed to the different algae growth phase (Chen et al, 2004) or water condition (Pan et al, 2011a) often led to the flocculation efficiency variable.…”

Removal of harmful cyanobacterial blooms in Taihu Lake using local soils III. Factors affecting the removal efficiency and an in situ field experiment using chitosan-modified local soils

“…The materials used here, such as clays, minerals, Taihu Lake local soils, chitosan and MA strains, were described in previous studies Zou et al, 2006). The treatment of the materials, the flocculation experiments, the instrumental settings, and the analytical procedures were the same as those described before Zou et al, 2006).…”

“…The treatment of the materials, the flocculation experiments, the instrumental settings, and the analytical procedures were the same as those described before Zou et al, 2006).…”